JPS6111779B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a resin sheet having a large number of protrusions on its surface, particularly a resin sheet in which the protrusions extend in different directions on the front and back surfaces.

A resin sheet having a large number of protrusions on its surface is already known. Such a sheet is, for example, sheet 1 shown in FIG. In FIG. 1, a large number of protrusions 2 extending parallel to each other are formed on only one side, and the other side is flat. A valley 3 is formed between adjacent protrusions 2. In sheet 1,
Both the protrusions 2 and the valleys 3 are oriented in the direction of arrow a.

A resin sheet 1 as shown in FIG. 1 can be easily produced by an extrusion method. For example, as shown in FIG. 2, a cylindrical object having protrusions 2 and valleys 3 is extruded from a die having an annular gap, the resulting cylindrical object is cut open, and the cylindrical object shown in FIG. 1 is extruded. A resin sheet 1 like this can be made.
The cap used in this case has an outer mold 4 and an inner mold 5.
An annular gap is formed between the outer mold 4 and the wall surface forming the gap, and valleys and peaks corresponding to the protrusions 2 and valleys 3 are formed along the circumferential direction.

Resin sheet 1 made using such a base
In this case, the extending directions of the protrusions 2 and valleys 3 all coincide with the extrusion direction a. Furthermore, in this method, since the cylindrical object is pulled in the extrusion direction, the resin molecules in the cylindrical object are always oriented in the extrusion direction a. As a result, the resin sheet with protrusions produced by such a method is likely to tear along the extrusion direction a. In particular, since the sheet becomes thinner at the valleys 3, it is likely to tear along the valleys 3. This was considered a drawback of the resin sheet with protrusions. Therefore, there has been a demand for a resin sheet with protrusions that does not have these drawbacks. This invention was created in response to such a demand.

The inventor thought of solving this problem by forming protrusions on the front and back surfaces of the sheet and making the extending directions of the protrusions on the front and back surfaces different. Ta. That is, as shown in FIG.
An attempt was made to improve this defect by setting the direction in which the protrusions 6 extend on the back surface as arrow b, and the direction in which the protrusions 6 on the back surface extend as arrow c, and making arrows b and c intersect.

The sheet shown in Figure 3 is obtained by cutting out the sheet shown in Figure 1 and then cutting out the sheet shown in Figure 1.
It can be made by placing the sheets back to back and gluing the back sides together. However, if sheets like the one shown in FIG. 1 are cut out and then pasted together, the pasting process takes time and cannot be easily produced. The present invention relates to a method for efficiently manufacturing a resin sheet with protrusions as shown in FIG.

The inventor discovered that in the extrusion method shown in FIG. 2, when the outer mold 4 is rotated, the protrusions 2 are oriented diagonally with respect to the direction of the arrow a, and the cylindrical product thus obtained is flattened. I noticed that when folded, the extending directions of the protrusions 2 cross each other. Therefore, if the cylindrical object obtained in this way is pressed to make it flat and the inner surfaces are fused or adhered to each other,
It has been found that a resin sheet with protrusions as shown in FIG. 3 can be easily obtained. This invention was made based on such knowledge.

This invention relates to a method for manufacturing a cylindrical molded body by extruding a thermoplastic resin softened by heating from a die having an annular gap, in which the tip of an outer mold constituting the annular gap is attached to a wall surface. , a large number of peaks or valleys are formed along the circumferential direction, the resin is extruded while rotating the outer mold around the axis of the annular gap, the extruded cylindrical molded product is flattened, and the inner surface is bonded or melted. The present invention relates to a method for manufacturing a resin sheet having protrusions, which is characterized in that the resin sheet is coated with ridges.

FIG. 4 is a partially cutaway perspective view showing a state in which a cylindrical molded body is produced by extruding resin while rotating the outer die of the die in the method of the present invention. Fifth
The figure is a partially cutaway perspective view showing a state in which a cylindrical molded body is flattened and its inner surface is adhered in the method of the present invention.

In FIG. 4, the cap has an inner mold 1 inside an outer mold 13.
4, an annular gap is formed therebetween, and the resin softened by heating is extruded from the annular gap. A large number of peaks and valleys are formed along the circumferential direction on the wall surface forming the annular gap at the tip of the outer mold 13. Therefore, when the resin is extruded from the annular gap, the resin is applied to the protrusion 11 where the valley was formed on the outer wall of the outer mold 13.
will be formed. At the same time, the resin forms valleys 12 between the protrusions 11.

The outer mold 13 is rotated in the direction of arrow d with the magnitude of arrow d. From the annular gap, resin is extruded in the direction of arrow a and in the size of arrow a, and a cylindrical molded body 10 is formed. Therefore, the protrusions 11 formed on the cylindrical molded body 10 by the valleys of the outer mold 13 are as a result of the combination of arrows a and d.
It extends along the direction of arrow b. In this way, a large number of protrusions 11 are formed on the outer surface of the cylindrical molded body 10 along the diagonal direction b with respect to the cylinder axis direction a.

In this way, a large number of protrusions 11 are arranged in a spiral pattern on the outer surface of the cylindrical molded body 10, but when the cylindrical molded body 10 is cut open and made into a planar shape, the protrusions 11
1 are lined up parallel to each other. However, if the cylindrical molded body 10 is crushed and flattened as it is, the protrusions 11 will extend in opposite directions on the front side and the back side. That is, as shown in FIG. 5, on the front side, the protrusion 11 extends in the direction of arrow b, but on the back side, the protrusion 11 extends in the direction of arrow c. Therefore, when the inner surfaces of the cylindrical molded body 10 are adhered together in a flattened state, the extending directions of the protrusions 11 will intersect on the front and back sides. In this way, a sheet with intersecting ridges can be easily obtained.

In order to bond the inner surfaces of the cylindrical molded body 10 together, it is convenient to do the following. The cylindrical molded body 10 extruded by the method shown in FIG. 4 is cooled from the outside. Then, the outer surface of the cylindrical molded body is first cooled. However, the inner surface of the cylindrical molded body 10 is still softened due to the delay in cooling. Therefore, when the cylindrical molded body 10 is crushed to make it flat, the protrusions on the outer surface do not deform because they are cooled, but the inner surfaces are in a softened state and are fused together and become integral. In this way, they can be easily pasted together.

In addition, in order to form a bonded body, it is also possible to once take out a cylindrical molded body, apply an adhesive to its inner surface, and bond the inner surfaces together. In this case, the cylindrical molded body may be slightly heated.

Various thermoplastic resins can be used in the method of this invention. The main resins that can be used are polyvinyl chloride, polyethylene, polypropylene, polystyrene, polyester, etc. The method of this invention includes not only the case where the resin is not made into a foam, but also the case where the resin is made into a foam. When it is made into a foam, the cells in the foam are elongated in the direction in which the protrusions 11 extend, and therefore the arrangement of resin molecules in the direction of the protrusions 11 is clearly recognized. Therefore, in the case of a foam, the direction in which the bubbles are stretched differs between one side and the opposite side of the laminated sheet.

As the blowing agent to be added when forming a foam, various known blowing agents can be used. Foaming agents can be broadly divided into those that are gaseous at room temperature;
There are three types: those that are liquid at room temperature and easily volatilize, and those that are solid at room temperature and decompose and generate gas when heated, and any of these can be used in the method of this invention. . As blowing agents that are gaseous at room temperature, nitrogen, carbon dioxide, propane, butane, etc. can be used, and as easily volatile liquids,
Aliphatic hydrocarbons such as pentane, hexane petroleum ether, halogenated hydrocarbons such as methylene chloride, trichloromonofluoroethane, trichlorotrifluoroethane can be used; as separate solid compounds, azo Azo compounds such as dicarbonamides can be used.

This invention method requires rotating a part of the outer mold, particularly the tip of the wall surface forming the annular gap. Attempts to rotate part of the cap have already been proposed to achieve other objectives. For example, when a non-foamed cylindrical film is formed by the extrusion inflation method and the formed film is wound into a roll, there are local differences in the thickness of the film, and the thick part of the film is 1 In order to avoid overlapping winding, it has been proposed to rotate the tip of the die forming the extrusion slot.

However, in this proposed method, the base to be rotated is provided with an annular gap of substantially equal width, and a large number of curved ridges are formed on the wall surface constituting the gap along the circumferential direction. It is not something that specifically has a valley and a valley. Furthermore, the purpose of the rotation is to improve the appearance of the wound film, and is not intended to provide protrusions or change the direction in which the protrusions extend. Also,
In the proposed method, the rotation is extremely slow, and it takes about 10 to 20 minutes to rotate the cap once. However, with this invented method, the rotation is fast,
It rotates once in less than a minute.

In the above description of FIG. 4, only the outer mold 13 is rotated, but if only the outer mold 13 is rotated, the pressed cylindrical molded body 10 tends to become twisted. Therefore, in order to prevent this twisting, it is preferable to rotate the inner mold 14 in the opposite direction to the outer mold 13. Among them, the inner mold 14 is
Linear velocity e in the opposite direction to the outer mold 13 and equal to
It is preferable to rotate at

In addition, in FIG. 4, the wall surface near the tip of the inner mold 14 is made into a perfect circle, and the wall surface has no ridges or valleys formed along the circumferential direction, but the wall surface of the inner mold 14 is Also, peaks or valleys may be formed. The number of peaks or valleys provided on the wall surface of the inner mold 14 does not need to be as large as the number of peaks or valleys provided on the wall surface of the outer mold 13, and the difference in height does not need to be so large. Inner mold 14
If peaks or valleys are provided here and there on the wall surface, when the cylindrical molded body 10 is flattened and the inner surfaces are bonded together, the peaks formed on one of the inner surfaces sink into the other, making the bonded surface strong. There are advantages to becoming

The rotating portion of the cap is the wall surface of the resin passage located near the tip of the cap. A portion of the rotating wall surface is provided with a number of peaks or valleys that bend along the circumferential direction. This peak or valley extends to some extent from the tip of the cap toward the back of the cap. The extending direction may coincide with the axial direction of the annular interval, or may be slightly inclined.

The ridges or valleys provided on the wall surface of the resin passage of the cap can also be viewed as mere kerfs. The kerf provided on the outer mold is a valley when viewed from the die, and the area other than the kerf becomes a ridge. The peaks or valleys are appropriately determined depending on the thickness of the resin sheet to be obtained. As shown in Fig. 5, take one sheet before pasting, let the thickness of the sheet at the bottom of the valley be T, and let the difference in height between the peak and valley be q,
If the distance between the peaks of adjacent mountains is P, then q is T
Preferably, P is in the range of 0.5 to 5 with respect to T, P is in the range of 2 to 10 with respect to T, q is in the range of 1 to 3 with respect to T, and P is set to be in the range of 3 to 8 with respect to T.

The rotational speed of the die is changed in accordance with the advancing speed of the resin in the die due to extrusion. In other words, the rotational speed is
Make it bigger accordingly. In this case, the relationship between the rotational speed of the cap and the advancing speed of the resin can be considered as follows. In FIG. 4, among the angles formed by the rotational linear speed d of the outer mold and the advancing speed a of the resin in the extrusion direction, when the angle β is used as a reference as shown in the figure, d/a=tanβ. Similarly, among the angles formed by the rotational linear velocity e of the inner mold and the advancing velocity a of the resin, the angle γ is
If it is taken as a standard, e/a=tanγ. Therefore, taking into account that d and e rotate in opposite directions, the larger the sum of the angles β and γ, the larger the ratio of the rotational speed to the extrusion speed. In particular, when the values of angle β and angle γ are both 45 degrees, the influence of rotational speed should be most significant. However, when using polyethylene and polystyrene as resins and making them into foams,
The effect of rotation was most pronounced when the sum of angles β and γ was in the range of 20 to 60 degrees.

According to the method of this invention, a ridge or valley that bends in the circumferential direction is provided on the outer mold wall surface at the tip of the die, and the tip of the die is rotated, thereby crushing and flattening the obtained cylindrical molded body. By simply bonding the inner surfaces together, it is possible to easily and continuously produce a resin sheet in which the extending directions of the protrusions intersect with each other on the front and back sides. Moreover, since the thus obtained sheet with ridges extends in different directions on the front and back sides, it is difficult to tear along one valley. In particular, as the tip of the mouthpiece rotates, the resin molecules are oriented in the direction in which the protrusions extend, so that even when a sheet is made from foam, it will not tear easily. Moreover,
Since the sheet is provided with ridges or valleys, the entire surface and back surface will not come into close contact with other objects, making it suitable as a cushion material. In particular, when using foamable resin as the resin,
Since the cushioning effect of the bubbles and the orientation of the bubbles are added, the obtained resin sheet with protrusions becomes even more excellent as a cushion material. As described above, the resin sheet obtained by the method of this invention has various advantages.

Next, an example of the method of this invention will be specifically explained with reference to Examples. In the following, parts simply mean parts by weight.

Example 1 Using low density polyethylene as the resin, the resin
After mixing 100 parts with 1 part of talc (bubble control agent), this mixture was heated at a rate of 15 kg for 1 hour with a diameter of 40 mm.
It was fed to a φ extruder. The temperature of the resin inside the extruder
The resin was heated to 180°C to melt it, and 12 parts of butane (a blowing agent) was press-fitted in the middle of the extruder, and the resin was cooled to 110°C at the tip of the extruder and extruded from the die.

The cap shown in FIG. 6 was used.
In FIG. 6, A is a vertical cross-sectional view of the cap, B is a cross-sectional view taken along line A and A in FIG. 6, and C is a partially enlarged view of FIG. The cap has an outer mold 13 and an inner mold 14.
An annular gap 15 is provided between the two, from which the resin is extruded. Further, the inner mold 14 was provided with a hole 16 in the center thereof which communicated with the outside air. At annular intervals, 65 kerf grooves F each having an isosceles triangular cross section were formed at equal intervals on the wall surface of the outer mold 13. Regarding the dimensions of the gap, the diameter of the annular gap 15 is approximately 60 mm, the width W is 0.5 mm, and the gap between the grooves M is
was 1.3 mm, the base N of the kerf F was 1.6 mm, the height K was 1.8 to 2.0 mm, and the depth L was 5 to 6 mm.

The resin was extruded while rotating the outer mold 13 and the inner mold 14 of this die in opposite directions at a rate of 3 revolutions per minute. As the resin exited the cap in a cylindrical shape, it foamed, increasing its thickness and significantly increasing its diameter. In this case, in order to increase the diameter and adjust the amount of gas contained within the cylindrical molded body,
Air was introduced through hole 16. The tip of the cylindrical molded product thus extruded was pinched between a pair of pinch rolls to make it flat, and while the inner surface of the molded product was still in a softened state, the inner surfaces were fused together.

The foam sheet thus obtained has a density of 0.033
g/cm ³ , the width of the sheet is 144 mm, the thickness between the valleys is 4 mm, and the height difference q is 1.6 mm. Both sides have protrusions with a triangular cross section, and the direction in which the protrusions extend is relative to the extrusion direction. Both were inclined at an angle of about 20 degrees, and the bubbles were also oriented at an angle of about 20 degrees with respect to the extrusion direction. Therefore, this sheet was difficult to tear along the valleys and was excellent as a cushion material.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of a conventional chevron-shaped resin sheet. FIG. 2 is a perspective view showing the main parts of a conventional method for manufacturing a chevron-shaped resin sheet. FIG. 3 is a partially cutaway perspective view of a chevron-shaped resin sheet that is the object of the method of the present invention. 4 and 5 are perspective views showing essential parts of the manufacturing method according to the present invention. FIG. 6 is a partially cutaway sectional view showing details of the base used in the method of the present invention.

Claims (1)

[Claims] 1. In a method for manufacturing a cylindrical molded body by extruding a thermoplastic resin softened by heating from a die having an annular gap, the tip of the outer mold forming the annular gap A large number of peaks or valleys are formed along the circumferential direction on the wall surface of the wall, the resin is extruded while rotating the outer mold around the axis of the annular gap, and the extruded cylindrical molded product is flattened to form an inner surface. A method for producing a resin sheet with protrusions, characterized by adhesion or fusing. 2. In a method for manufacturing a cylindrical molded body by extruding a thermoplastic resin softened by heating from a die having an annular gap, a circular wall is formed on the wall surface near the tip of the outer mold constituting the annular gap. A large number of ridges and troughs are formed along the circumferential direction, and ridges or troughs are also formed in the circumferential direction on the wall surface at the tip of the inner mold that constitutes the annular gap, and the outer mold is aligned with the axis of the annular gap. It is characterized by extruding resin while rotating it, flattening the extruded resin, and bonding or fusing the inner surface.
A method for manufacturing a resin sheet with protrusions. 3. The method according to claim 1 or 2, wherein a foaming agent is included in the resin and the resin sheet with protrusions is made of a closed-cell foam. 4. The method according to any one of claims 1 to 3, wherein the inner mold is rotated in the opposite direction to the outer mold. 5. The method according to claim 4, wherein the outer mold and the inner mold are rotated so that the linear velocity on the wall surface of the annular gap is equal to the advancing speed in the extrusion direction within the annular gap.